You need to purchase an expensive chemical for a series of enzyme assays. Sigma Chemical Company sells the chemical in 1g ($30), 5g ($120), 10g ($200), and 25g ($400) vials. You will perform 40 assays. Each assay requires 3 ml of a 250mM solution of the chemical (M. W. = 156 g/mole). Which vial (s) is the best choice for your limited budget?

Question

Jefferson Santana

Chemistry

3 October, 22:40

You need to purchase an expensive chemical for a series of enzyme assays. Sigma Chemical Company sells the chemical in 1g ($30), 5g ($120), 10g ($200), and 25g ($400) vials. You will perform 40 assays. Each assay requires 3 ml of a 250mM solution of the chemical (M. W. = 156 g/mole). Which vial (s) is the best choice for your limited budget?

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Answers (1)

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Leila Rosario · Answer 1

5g ($120)

Explanation:

The amount of chemical needed for assay is 3 ml of 250 mM solution of a chemical

Molarity (M) = number of moles / volume in L

number of mole = M * volume in L

M of the chemical = 250 mM = 250 / 1000 = 0.25 M

number of moles = 0.25 * (3 / 1000) in L = 0.00075 m

mass of the chemical needed = 0.00075 * molar mass = 0.00075 * 156 = 0.117 g for each assay.

mass needed for 40 assay = 40 * 0.117 = 4.68 g

It is therefore wise for him to buy the 5 g ($ 120), though the 10 g and 25 g yields better prices per gram, they much more than what he needed for the assay.